[PATCH v5 1/2] drm: Add per-plane pixel blend mode property
Lowry Li
lowry.li at arm.com
Thu Aug 23 08:30:19 UTC 2018
Pixel blend modes represent the alpha blending equation
selection, describing how the pixels from the current
plane are composited with the background.
Adds a pixel_blend_mode to drm_plane_state and a
blend_mode_property to drm_plane, and related support
functions.
Defines three blend modes in drm_blend.h.
Changes since v1:
- Moves the blending equation into the DOC comment
- Refines the comments of drm_plane_create_blend_mode_property to not
enumerate the #defines, but instead the string values
- Uses fg.* instead of pixel.* and plane_alpha instead of plane.alpha
Changes since v2:
- Refines the comments of drm_plane_create_blend_mode_property:
1) Puts the descriptions (after the ":") on a new line
2) Adds explaining why @supported_modes need PREMUL as default
Changes since v3:
- Refines drm_plane_create_blend_mode_property(). drm_property_add_enum()
can calculate the index itself just fine, so no point in having the
caller pass it in.
- Since the current DRM assumption is that alpha is premultiplied
as default, define DRM_MODE_BLEND_PREMULTI as 0 will be better.
- Refines some comments.
Changes since v4:
- Adds comments in drm_blend.h.
- Removes setting default value in drm_plane_create_blend_mode_property()
as it is already in __drm_atomic_helper_plane_reset().
- Fixes to use state->pixel_blend_mode instead of using
plane->state->pixel_blend_mode in reset function.
- Rebases on drm-misc-next.
Reviewed-by: Liviu Dudau <liviu.dudau at arm.com>
Signed-off-by: Lowry Li <lowry.li at arm.com>
---
drivers/gpu/drm/drm_atomic.c | 4 ++
drivers/gpu/drm/drm_atomic_helper.c | 1 +
drivers/gpu/drm/drm_blend.c | 123 ++++++++++++++++++++++++++++++++++++
include/drm/drm_blend.h | 6 ++
include/drm/drm_plane.h | 9 +++
5 files changed, 143 insertions(+)
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 3eb061e..d0478ab 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -895,6 +895,8 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
state->src_h = val;
} else if (property == plane->alpha_property) {
state->alpha = val;
+ } else if (property == plane->blend_mode_property) {
+ state->pixel_blend_mode = val;
} else if (property == plane->rotation_property) {
if (!is_power_of_2(val & DRM_MODE_ROTATE_MASK)) {
DRM_DEBUG_ATOMIC("[PLANE:%d:%s] bad rotation bitmask: 0x%llx\n",
@@ -968,6 +970,8 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
*val = state->src_h;
} else if (property == plane->alpha_property) {
*val = state->alpha;
+ } else if (property == plane->blend_mode_property) {
+ *val = state->pixel_blend_mode;
} else if (property == plane->rotation_property) {
*val = state->rotation;
} else if (property == plane->zpos_property) {
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 6dd5036..284a5d2 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -3569,6 +3569,7 @@ void __drm_atomic_helper_plane_reset(struct drm_plane *plane,
/* Reset the alpha value to fully opaque if it matters */
if (plane->alpha_property)
state->alpha = plane->alpha_property->values[1];
+ state->pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
plane->state = state;
}
diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
index a16a74d..402b62d 100644
--- a/drivers/gpu/drm/drm_blend.c
+++ b/drivers/gpu/drm/drm_blend.c
@@ -107,6 +107,52 @@
* planes. Without this property the primary plane is always below the cursor
* plane, and ordering between all other planes is undefined.
*
+ * pixel blend mode:
+ * Pixel blend mode is set up with drm_plane_create_blend_mode_property().
+ * It adds a blend mode for alpha blending equation selection, describing
+ * how the pixels from the current plane are composited with the
+ * background.
+ *
+ * Three alpha blending equations are defined:
+ *
+ * "None":
+ * Blend formula that ignores the pixel alpha::
+ *
+ * out.rgb = plane_alpha * fg.rgb +
+ * (1 - plane_alpha) * bg.rgb
+ *
+ * "Pre-multiplied":
+ * Blend formula that assumes the pixel color values
+ * have been already pre-multiplied with the alpha
+ * channel values::
+ *
+ * out.rgb = plane_alpha * fg.rgb +
+ * (1 - (plane_alpha * fg.alpha)) * bg.rgb
+ *
+ * "Coverage":
+ * Blend formula that assumes the pixel color values have not
+ * been pre-multiplied and will do so when blending them to the
+ * background color values::
+ *
+ * out.rgb = plane_alpha * fg.alpha * fg.rgb +
+ * (1 - (plane_alpha * fg.alpha)) * bg.rgb
+ *
+ * Using the following symbols:
+ *
+ * "fg.rgb":
+ * Each of the RGB component values from the plane's pixel
+ * "fg.alpha":
+ * Alpha component value from the plane's pixel. If the plane's
+ * pixel format has no alpha component, then this is assumed to be
+ * 1.0. In these cases, this property has no effect, as all three
+ * equations become equivalent.
+ * "bg.rgb":
+ * Each of the RGB component values from the background
+ * "plane_alpha":
+ * Plane alpha value set by the plane "alpha" property. If the
+ * plane does not expose the "alpha" property, then this is
+ * assumed to be 1.0
+ *
* Note that all the property extensions described here apply either to the
* plane or the CRTC (e.g. for the background color, which currently is not
* exposed and assumed to be black).
@@ -448,3 +494,80 @@ int drm_atomic_normalize_zpos(struct drm_device *dev,
return 0;
}
EXPORT_SYMBOL(drm_atomic_normalize_zpos);
+
+/**
+ * drm_plane_create_blend_mode_property - create a new blend mode property
+ * @plane: drm plane
+ * @supported_modes: bitmask of supported modes, must include
+ * BIT(DRM_MODE_BLEND_PREMULTI). Current DRM assumption is
+ * that alpha is premultiplied, and old userspace can break if
+ * the property defaults to anything else.
+ *
+ * This creates a new property describing the blend mode.
+ *
+ * The property exposed to userspace is an enumeration property (see
+ * drm_property_create_enum()) called "pixel blend mode" and has the
+ * following enumeration values:
+ *
+ * "None":
+ * Blend formula that ignores the pixel alpha.
+ *
+ * "Pre-multiplied":
+ * Blend formula that assumes the pixel color values have been already
+ * pre-multiplied with the alpha channel values.
+ *
+ * "Coverage":
+ * Blend formula that assumes the pixel color values have not been
+ * pre-multiplied and will do so when blending them to the background color
+ * values.
+ *
+ * RETURNS:
+ * Zero for success or -errno
+ */
+int drm_plane_create_blend_mode_property(struct drm_plane *plane,
+ unsigned int supported_modes)
+{
+ struct drm_device *dev = plane->dev;
+ struct drm_property *prop;
+ static const struct drm_prop_enum_list props[] = {
+ { DRM_MODE_BLEND_PIXEL_NONE, "None" },
+ { DRM_MODE_BLEND_PREMULTI, "Pre-multiplied" },
+ { DRM_MODE_BLEND_COVERAGE, "Coverage" },
+ };
+ unsigned int valid_mode_mask = BIT(DRM_MODE_BLEND_PIXEL_NONE) |
+ BIT(DRM_MODE_BLEND_PREMULTI) |
+ BIT(DRM_MODE_BLEND_COVERAGE);
+ int i;
+
+ if (WARN_ON((supported_modes & ~valid_mode_mask) ||
+ ((supported_modes & BIT(DRM_MODE_BLEND_PREMULTI)) == 0)))
+ return -EINVAL;
+
+ prop = drm_property_create(dev, DRM_MODE_PROP_ENUM,
+ "pixel blend mode",
+ hweight32(supported_modes));
+ if (!prop)
+ return -ENOMEM;
+
+ for (i = 0; i < ARRAY_SIZE(props); i++) {
+ int ret;
+
+ if (!(BIT(props[i].type) & supported_modes))
+ continue;
+
+ ret = drm_property_add_enum(prop, props[i].type,
+ props[i].name);
+
+ if (ret) {
+ drm_property_destroy(dev, prop);
+
+ return ret;
+ }
+ }
+
+ drm_object_attach_property(&plane->base, prop, DRM_MODE_BLEND_PREMULTI);
+ plane->blend_mode_property = prop;
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_plane_create_blend_mode_property);
diff --git a/include/drm/drm_blend.h b/include/drm/drm_blend.h
index 330c561..88bdfec 100644
--- a/include/drm/drm_blend.h
+++ b/include/drm/drm_blend.h
@@ -27,6 +27,10 @@
#include <linux/ctype.h>
#include <drm/drm_mode.h>
+#define DRM_MODE_BLEND_PREMULTI 0
+#define DRM_MODE_BLEND_COVERAGE 1
+#define DRM_MODE_BLEND_PIXEL_NONE 2
+
struct drm_device;
struct drm_atomic_state;
struct drm_plane;
@@ -52,4 +56,6 @@ int drm_plane_create_zpos_immutable_property(struct drm_plane *plane,
unsigned int zpos);
int drm_atomic_normalize_zpos(struct drm_device *dev,
struct drm_atomic_state *state);
+int drm_plane_create_blend_mode_property(struct drm_plane *plane,
+ unsigned int supported_modes);
#endif
diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
index 8a152dc..35ef64a 100644
--- a/include/drm/drm_plane.h
+++ b/include/drm/drm_plane.h
@@ -117,6 +117,7 @@ struct drm_plane_state {
* details.
*/
u16 alpha;
+ uint16_t pixel_blend_mode;
/**
* @rotation:
@@ -659,6 +660,14 @@ struct drm_plane {
* drm_plane_create_rotation_property().
*/
struct drm_property *rotation_property;
+ /**
+ * @blend_mode_property:
+ * Optional "pixel blend mode" enum property for this plane.
+ * Blend mode property represents the alpha blending equation selection,
+ * describing how the pixels from the current plane are composited with
+ * the background.
+ */
+ struct drm_property *blend_mode_property;
/**
* @color_encoding_property:
--
1.9.1
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